Denim washing Process

Denim washing is aesthetic finish given to denim fabric to enhance the demand and to provide strength. Dry denim as opposed to washed denim is a denim fabric that is not washed after being dyed during its production.

Much of the appeal of dry denim lies in the fact that with time fabric will fade in a manner similar to that which artificially distressed denim attempts to replicate . With dry denim however such fading is affected by the body of the person who wears jeans and the activities of their daily life. This creates what many fell to be more natural, unique look than pre distressed denim.

It is a new technology by which out look , size , comfort ability and fashion of a garment are changed or modified . This technology was first appeared in Bangladesh in 1988.Before that washing was carried out only in Hong Kong and Singapore , i.e. after sewing garments were sent to abroad for washing and again brought here back for finishing , tagging and packing . As a result , extra overhead cost ( freight , washing charge, time consumptions ) was drawn in.

The changes occur due to he following actions :

1. Mechanical / rubbing / abrasion between garments to garments .
2. Garments to machine; and
3. Chemical action.

Objects of garments washing:

• To develop softness in garments : Size materials applied during manufacturing present in the fabric are removed which enhances soft hand feel . Additional softness may be attained by using softener .
• To introduce fading effect : Dyes or pigments are present in the fabric , used during coloration, are washed out locally or partially which result fading or worn out effects in the garments.
• To create new fashion : Washing Process of garments bring different outlook ( faded, color tinted etc ) thus creating new fashion for the new generation especially for teenagers.

• To satisfy the consumer :As the contraction or extraction (shrinkage ) occur due to washing , the wearer can use the garments after purchase satisfactory

Advantages of garments washing:

The following advantages are obtained could be gained from the garments washing—

• Removal of starch or size materials make the fabric soft hand feel.
• Softness could be increased by the addition of softener just at the last stage of washing.
• Dirt, spots, impurities, gum etc, if accumulated in the garments during manufacturing could be removed.
• During washing shrinkage may takes place, therefore after washing there is no possibility to create such problem.
• Washed garments could be worn directly after purchase .
• Faded or worn out effect could introduced to the garments which creates new fashion
• Similar outlook can be obtained by different washing techniques.
• Comparatively lower capital is required to set up a washing plant.
• Lower land space and least manpower cost are required to run a washing plant.

Unavoidable changes / limitations of garments washing

Like other processes the garments washing is also not without some limitations. They included as below-

• Garments size change : Size change takes place due to shrinkage properties of fabric . The amount of shrinkage properties of fabric determine the size change of the garments.
• Size material is partly removed : Unfixed dyes may remain on the surface of the garments and it is necessary to remove completely after washing.

The history of denim

A popular conception of the entomology of the denim is that it is a contraction or derivative of the french term SERGE DE NIMES. Denim was traditionally colored blue with indigo dye to make blue “Jeans“

Though “Jean“ then denoted a different , lighter cotton textile ; the contemporary use of jean comes from the French word for Genoa ,Italy,(Genes ) , from which the first denim trousers were made .

Similarly woven traditional American cotton textile is the diagonal warp-striped hickory cloth that was once associated with railroad men’s overalls, in which blue or black contrasting with undyed white threads from the woven pattern . Records of a group of New Yorkers headed for the California gold fields in 1849 show that they took along four “hickory shirts “ apiece. Hickory cloth would later furnish the material for some “fatigue” pantaloons and shirts in the American civil war.

Introduction

Denim is a rugged twill textile , in which the weft passes under the two or more warp yarns, producing the familiar diagonal ribbing identifiable on the revere of the fabric.

Characteristics of denim fabric:

1. Warp yarns are colored (usually with indigo, vat, blue or sulphur black );
2. Structure : right hand or left hand twill, i.e. z/s-twill of 2/1 or 3/1construction;
3. Usually made of cotton yarns of coarser count (7^s, 10^s, 14^s, 16^s, etc )
4. Coarser cloth ( weight lies between 6-14 oz/sq.yds ) and used for pant and warm jackets;
5. Rotor yarn are usually used.

Specification of typical denim fabric =7×1072×56 × 58”

Classification of denim fabric :

1.As per weight /unit area.

1.  Light weight : 4.5 to 7 oz/sq.yd
2. Medium weight : 7 to 10 oz/sq.yd
3. Heavy weight: 11 and above.

2. As per hue and color .

1. Indigo vat.
2. Sulphur black.
3. Pigment.

3.As per slub yarns :

1. Warp yarns are slub only.
2. Weft yarn are slub only.
3. Cross Hatch : both way slub i.e. both warp and weft yarn are slub.

4.As per fabric structure /design:

1. Plain.
2. Twill (S-twill, Z-twill, herringbone or zigzag twill )

Jean:

comes from French word “Genes” used to describe the pants sailors from Genoa, Italy, once wore. While the historical definition implied that all jeans were made of denim , jeans today usually refer to a garments that has five pockets (two in the front, two in the back and small change pocket on the front right pocket ) and this style can be made using any kinds of fabrics be it corduroy, twill, or bull denim.

Jeans:

Long , narrow pants, especially for women , manufactured by diagonal weave cotton fabric , named after where the texture originally were manufactured, the town Genoa, Italy . Jeans are pants or trousers, made from denim . Mainly designed for work, they became popular among teenagers starting in the 1950. Historic brands include levi’s American population spent more than $14 billion on jeans in 2004.

Bull Denim :

Piece-dyed cotton twill made from coarse yarn to resemble denim, however , the warp yarns are not dyed with indigo before weaving.

Bell Bottom:

A jeans style born in the late 60s, 70s. Bell-bottom are trousers that become wider from the knees downward. Tight at the waist (some times lowered ) and at the thighs , the trousers flare out from the knee to make a come back at the end of the 80s, but didn’t quite catch on.

Cross Hatch:

An effect of the denim weave created by using uneven yarn in the weft direction, combined with uneven yarns in the warp direction.

Hipster jeans :

A style of jeans that start about 10 centimeters below the navel.

Rigid Denim:

Describe unwashed denim. Most denim garments are typically prewashed before going to retail.

Low rise Jeans:

Low rise Jeans, worn by both men and women, are jeans intended to sit low on or below, the hips. They are also called low cut jeans , hipsters, hip-huggers and lowriders . Usually they sit at least 8cm (3”) lower than belly button.

Chemical components:

A typical denim garment before wash consists of the following chemical components-

Component	Purpose	Application point
ModifiedStarch/ PVA	Improve warp yarn strength	During sizing of warp sheet
Binder/guar gum/CMC	Lubricant/ adhesive/ humectants	do
Dyes (vat, sulphur )	or coloration	During dyeing of warp sheet
Dyes fixatives	Improve color and wash fastness	Do
Silicon	Defoamer	Both during sizing and dyeing

Modified corn starch/PVC	For stiffness and hand stability	Do
DOSS(Di-octyl-sulpho-polyethyene)	Water	Do
High density polyethyene	Sanforizing and sewing lubricant	Do
Mineral oil and/or ester	Sanforizing lubricant	Do
Silicon	Improve hand feel and sew ability	Do

TYPES OF DENIM WASH

Denim washes are of following two type :–

1. Chemical washes

• Denim bleaching
• Enzyme wash
• Acid wash

1. Mechanical washes

• Stone wash
• Microsanding

DENIM BLEACHING

In the process a strong oxidative bleaching agent like sodium hypochlorite or KMnO₄ is added during the washing with or without stone addition. Discoloration produced is usually more apparent depending on strength on the bleach liquor quality, temperature and treatment time. It is preferable to have strong bleach with short treatment time.

Care should be taken for the bleached goods so that they should be adequately antichlored or after washed with peroxide to minimize yellowing. Materials should be carefully stored before processing for color uniformity,

Process cycle :

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water (liquor ratio 1:5) and start the machine running(12-15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Step # 2 (Bleaching)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm ) and add soda ash (Na₂CO₃) to liquor (2% i.e. 2kg) ;
• Add costic soda (NaOH) to liquor (2% i.e. 2kg) ;
• Add bleaching chemical (H₂O₂) to liquor (5ml per liter, i.e. 2.5 liters) ;
• Add stabilizer to liquor (2ml per liter, i.e. 1 liter) ;
• Supply steam to raise temp.(70°-80⁰C) ;
• Continue the process for 60 to 70 min. and drain the liquor ;
• Hot wash (at 60°C for 5 minutes).

Step # 3 ( Nutralization )

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 liters );
• Start m/c running ( 12 to 15 rpm );
• Add acetic acid ( CH₃COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);
• Continue the process for 10-15 min and then drain the liquor.

Step # 4 ( Brightening treatment)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add Fluorescent Whitening agent/Fluorescent Brightening agent to liquor (% as required );
• Supply steam to raise temperature (80⁰C);
• Continue the process for 10 min and then drain the liquor.

Step # 5 (Softening)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );

• Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);
• Supply steam to raise the temperature (as required 40⁰ to 60⁰C );
• Continue the process for 5 minutes and then drain the liquor and unload the garments.

Limitations of denim bleaching :

1. Process is difficult to control i.e. difficult to reach the same level of bleaching in repeated runs.
2. When desired level bleaching reached the time span available to stop the bleaching is very narrow. Due to harshness of chemical, it may cause damage to cellulose resulting in severe strength losses and or breaks or pinholes at the seam, pocket, etc.
3. Harmful to human health and causes corrosion to stainless steal.
4. Required antichlor treatment.
5. Problem of yellowing is very frequent due to residual chlorine.
6. Chlorinated organic substances occur as abundant products in bleaching and pass into the effluent where they cause severe environmental pollution.

ENZYME WASH

It is environmentally friendly wash. It involves the application of organic enzymes that eat away at the fabric, i.e. the cellulose. When the desired color is achieved, the enzyme can be stopped by changing the alkalinity of the bath or its temperature. Post treatment includes final ringing and softening cycle. The effects produced by cellulose enzyme are :—-

1. Use of cellulose making the seams, hems, and pockets more noticeable;
2. Salt paper effect is color contrast effect.
3. Faded garment washed with acid cellulose enzyme provides less color contrast in proportion to garment washed neutral cellulose enzymes.

Garment load size of the m/c is 35-40 jeans per m/c and it cannot be overloaded.

ACID WASH

It is done by tumbling the garments with pumice stones presoaked in a solution of sodium hypochlorite or potassium permanganate for localized bleaching resulting in a non uniform sharp blue/white contrast. In this wash the color contrast of the denim fabric can be enhanced by optical brightening. The advantage of this process is that it saves water as addition of water is not required.

It consists of soaking pumice stones with chlorine and using their abrasive power to bleach jeans into sharp contrasts. Also known as moon, fog, marble, ice and frosted.

Process cycle :

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;
• Start machine running (12 to 15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash at temp. of 40°C to 50°C for 5 minutes.

Step # 2 ( Bleaching)

To carry out the Bleaching process , the following two steps are to be passed over :

Step # A

• Take stone of some volume of the volume of garments ;
• Soak the sfone with the following chemical solution for 2 to 3 minutes ;

Water 100 litres

Potassium permanganate 1 kg

Phosphoric acid 300 ml (3ml per litres)

• Here the porous of stones are dried in the open air for 60 to 90 min.

Step # B

• Load the garments treated in step # 1 and step # 2 in a dry m/c. Lot size should be 20 to 30kg.
• Run the m/c for 5 to 7 minutes. Due to the rotation of m/c the socked stones will hit the garments surfaces and the chemicals in the stone will destroy color of the fabric. Multilayer fabric areas like collar, cuff, pocket, pocket side seam etc. area will be brushed more than the single layer areas, therefore more fading effect will be produced in those areas resulting new color effect in the garments.
• Unload the garments and separate the stones from the batch.
• In this stage KMnO₄ and H₃PO₄ reacts with each other and gives Oxygen which oxidize the color. Here a byproduct MnO₂ is produced which should be neutralized.

6KMnO₄ + 4H₃PO₄ = 2K₃PO₄ + Mn₃(PO₄)₂ + 6H₂O + 3MnO₂ + 2O₂

• This MnO₂ is solubilized by Sodium Metabisulfite (Na₂S₂O₅).

Na₂S₂O₅ + H₂O = 2NaHSO₃

NaHSO₃ + MnO₂ = MnSO₄ + NaOH

• Load the garments to the m/c ;
• Add water into the m/c (1:5 liquor ratio, i.e. 500 litres) ;
• Continue the process (12 to 15 rpm) ;
• Add sodium metabisulfite (1 to 2 gpl, i.e. 500 g to 1kg) ;
• Continue the process for 5 to 10 min and then drain the liquor ;
• Hot wash (at 40^o to 50^o C for 5 minutes).

Step # 3 ( Nutralization )

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );
• Add acetic acid ( CH₃COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);
• Continue the process for 10-12 min and then drain the liquor.

Step # 4 ( Brightening treatment)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add Fluorescent Whitening agent/Fluorescent Brighting agent to liquor (% as required );
• Supply steam to raise temperature (80⁰C);
• Continue the process for 10 min and then drain the liquor.

Step # 5 (Softening)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );

• Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);
• Supply steam to raise the temperature (as required 40⁰ to 60⁰C );
• Continue the process (5 minutes) ;
• Drain the liquor and unload the garments.

Limitations of acid wash :

• Acid washed ,indigo dyed denim has a tendency to yellow after wet processing.
• The major cause is residual manganese due to incomplete neutralization, washing or rinsing.

Remedy :

• Manganese is effectively removed during laundering with addition of ethylene-diamine-tetra-acetic acid as chelating agent.
• Acid washing jeans avoided some of problems of stone wash, but come with added danger, expenses and pollution.

STONE WASH

In the process of stone washing, freshly dyed jeans are loaded into large washing machines and tumbled with pumice stone or volcanic rock to achieve a soft hand and desirable look. Variations in compositions, hardness, size shape and porosity make these stone multifunctional. The process is quite expensive and requires high capital investment. Pumice stone give the additional effect of a faded or worn look as it abrades the surface of the jeans like sandpaper, removing some dye particles from the surfaces of the yarn.

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;
• Start machine running (12 to 15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Step # 2 (Stone wash)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add pumice stone half of the volume of garments (30 to 15 kg) ;
• Start machine running (12 to 15 rpm) ;
• Add bleaching powder to liquor (4% i.e. 4kg) ;
• Add soda ash (Na₂CO₃) to liquor (8% i.e. 8kg) ;
• Continue the process for 20 min to 40 min and then drain the liquor ;
• Hot wash (at 40°C to 50°C for 5 minutes).

Step # 5(Softening)

¤Add water into the machine(1:5 liquor ratio, i,e. 500 liters).

¤Start machine running (12 to 15 rpm).

¤Add softener to the liquor (0.1 to 0.5%, i,e. 100 g to 500 g).

¤Supply steam to raise the temp. (as required 40° to 60°C).

¤Continue the process (5 min).

¤Drain the liquor and unload the garments .

PUMICE STONE:

These are silica-rich, viscous, high temp. melt product of explosive eruption during ascent and expulsion of the earth. These are light weight , highly porous , rocky substances which will float on water . Major pumice stones supplier countries are USA, Turkey, Italy, Iceland , New Zealand, Japan , Indonesia and Philippines. This is one of the important components in the of stone washed apparels. It is used to abrade the surface of the fabric to obtain a surface pattern effect with colour contrast and softer hand. Since the degree of abrasion may varies in different parts of a garments such as trouser leg, button slay and seaming parts, a number of neutral patterns can be formed.

The degree of wash effect depends on stone size , stone ratio , liquor ratio , duration of treatment , amount of garments loaded , garments GSM, etc. Stone size varies from 1 cm diameter to 7 cm . But other washes like sand wash , micro wash, micro sand wash are now referring to use very small size pumice stones .

Selection of stone:

Stone should be selected of the proper hardness , shape and size for the particular end product . It should be noted that large , hard stones last longer and may be suited for heavy weight fabrics only. Smaller , softer stones would be used for light weight fabrics and more delicate items. Stone wt. / fabric wt. = 0.5 to 3 it depends on the degree of abrasion needed to achieve the desired result. Stones can be reused until they completely disintegrate or wash down the drain.

Problem caused by stones:

¤Damage to wash machineries and garment due to stone to machine and machine to stone abrasion.

¤Increase in labor to remove dust form finished garments .

¤Water pollution during disposal of used liquor.

¤Back staining and re-deposition.

Back staining or Re-deposition: The dye removed from denim material after the treatment with cellulose or by a conventional washing process may cause “back staining “ or “re-deposition”. Re-coloration of blue threads and blue coloration of white threads, resulting in less contrast between blue and white threads.

Remedy of back staining :

¤Adding dispersion/suspension agent to wash cycle. ¤Intermediate replacement of wash liquor. ¤Using alkaline detergent like sodium per borate with optical brightener as after wash.

LIMITATION OF STONE WASHING

# Quality of the abrasion process is difficult to control outcome of a load of jeans is never uniform, little percentage always getting ruined by too much abrasion.

# The process is non selective.

# Metal buttons and rivets on the jeans in the washing machines get abraded .

# This reduces quality of the products and life of equipment, and increases production costs.

# Stones may turn into powder during the process of making the garment grayish in color and rough too.

# provides rougher feel than enzyme wash.

# Stone may lead the harm to machine parts.

Microsanding

A fabric finishing process where fabrics are sanded (real sandpaper) to make the surface soft without hair. Can be performed before or after dyeing. In this fabric treatment process, a series of cylindrical rolls in a horizontal arrangement, either wrapped with an abrasive paper or chemically coated with an abrasive are used to create a soft, sueded hand. The denim is pulled over the face of the sand rollers creating a raised surface finishing. Some color reduction is experienced.

There are 3 ways for this technique:

1. Sandblasting.

2. Machine sanding.

3. Hand sanding or hand brushing.

Used in various ways:

# Flat surfaces (tables, ironing boards).

# On the dummy (inflatable dummies, sometimes standing, sometimes flat, sometimes seated).

# Various templates can be used to create a 3D effect.

Sand blasting

Jeans wear treatment that removes color from certain areas, either all over or placed and gives the garment additional softness. Sand is actually shot at the garment with a powerful spray gun. Recent technology has introduced “automatic” sandblasting, in which the jeans hang and rotate continuously.

1. It is purely mechanical process, not using in chemicals.
2. It is a water free process therefore no drying required.
3. Varity of distressed or abraded looks possible.
4. Any number of designs could be created by special techniques.

It is a process applied on denim fabric garments to get heavy faddy effects on particular points. Sand blasting technique is based on blasting an abrasive material in granular, powdered or other form through a nozzle at very high speed and pressure onto specific areas of garment surface to be treated to give the desired distressed/abraded/ used look.

PROCESS:

1. Individual garment to be processed is taken on a table.
2. Air compressor is started and pressure to maintained between 3-4 kg/sq.cm. Air compressor then stores air in the machine cylinder.
3. Aluminum sand or silicon sand, Al₂(SiO₄)_3, is than taken in the chamber of the blasting machine.
4. Sand and compressed air is than sprayed over the garments at specific points by hand spray pipe.
5. Sand pass into the machine by regulating system. The machine comprises a blasting regulator and a hand regulator to control the amount of sand and compressed air respectively.

`

Modified corn starch/PVC	For stiffness and hand stability	Do
DOSS(Di-octyl-sulpho-polyethyene)	Water	Do
High density polyethyene	Sanforizing and sewing lubricant	Do
Mineral oil and/or ester	Sanforizing lubricant	Do
Silicon	Improve hand feel and sew ability	Do

TYPES OF DENIM WASH:

Denim washes are of following two type :–

1. Chemical washes

• Denim bleaching
• Enzyme wash
• Acid wash

1. Mechanical washes

• Stone wash
• Microsanding

DENIM BLEACHING:

In the process a strong oxidative bleaching agent like sodium hypochlorite or KMnO₄ is added during the washing with or without stone addition. Discoloration produced is usually more apparent depending on strength on the bleach liquor quality, temperature and treatment time. It is preferable to have strong bleach with short treatment time.

Care should be taken for the bleached goods so that they should be adequately antichlored or after washed with peroxide to minimize yellowing. Materials should be carefully stored before processing for color uniformity,

Process cycle :

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water (liquor ratio 1:5) and start the machine running(12-15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Step # 2 (Bleaching)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm ) and add soda ash (Na₂CO₃) to liquor (2% i.e. 2kg) ;
• Add costic soda (NaOH) to liquor (2% i.e. 2kg) ;
• Add bleaching chemical (H₂O₂) to liquor (5ml per liter, i.e. 2.5 liters) ;
• Add stabilizer to liquor (2ml per liter, i.e. 1 liter) ;
• Supply steam to raise temp.(70°-80⁰C) ;
• Continue the process for 60 to 70 min. and drain the liquor ;
• Hot wash (at 60°C for 5 minutes).

Step # 3 ( Nutralization )

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 liters );
• Start m/c running ( 12 to 15 rpm );
• Add acetic acid ( CH₃COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);
• Continue the process for 10-15 min and then drain the liquor.

Step # 4 ( Brightening treatment)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add Fluorescent Whitening agent/Fluorescent Brightening agent to liquor (% as required );
• Supply steam to raise temperature (80⁰C);
• Continue the process for 10 min and then drain the liquor.

Step # 5 (Softening)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );

• Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);
• Supply steam to raise the temperature (as required 40⁰ to 60⁰C );
• Continue the process for 5 minutes and then drain the liquor and unload the garments.

Limitations of denim bleaching :

1. Process is difficult to control i.e. difficult to reach the same level of bleaching in repeated runs.
2. When desired level bleaching reached the time span available to stop the bleaching is very narrow. Due to harshness of chemical, it may cause damage to cellulose resulting in severe strength losses and or breaks or pinholes at the seam, pocket, etc.
3. Harmful to human health and causes corrosion to stainless steal.
4. Required antichlor treatment.
5. Problem of yellowing is very frequent due to residual chlorine.
6. Chlorinated organic substances occur as abundant products in bleaching and pass into the effluent where they cause severe environmental pollution.

ENZYME WASH

It is environmentally friendly wash. It involves the application of organic enzymes that eat away at the fabric, i.e. the cellulose. When the desired color is achieved, the enzyme can be stopped by changing the alkalinity of the bath or its temperature. Post treatment includes final ringing and softening cycle. The effects produced by cellulose enzyme are :—-

1. Use of cellulose making the seams, hems, and pockets more noticeable;
2. Salt paper effect is color contrast effect.
3. Faded garment washed with acid cellulose enzyme provides less color contrast in proportion to garment washed neutral cellulose enzymes.

Garment load size of the m/c is 35-40 jeans per m/c and it cannot be overloaded.

ACID WASH

It is done by tumbling the garments with pumice stones presoaked in a solution of sodium hypochlorite or potassium permanganate for localized bleaching resulting in a non uniform sharp blue/white contrast. In this wash the color contrast of the denim fabric can be enhanced by optical brightening. The advantage of this process is that it saves water as addition of water is not required.

It consists of soaking pumice stones with chlorine and using their abrasive power to bleach jeans into sharp contrasts. Also known as moon, fog, marble, ice and frosted.

Process cycle :

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;
• Start machine running (12 to 15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash at temp. of 40°C to 50°C for 5 minutes.

Step # 2 ( Bleaching)

To carry out the Bleaching process , the following two steps are to be passed over :

Step # A

• Take stone of some volume of the volume of garments ;
• Soak the sfone with the following chemical solution for 2 to 3 minutes ;

Water 100 litres

Potassium permanganate 1 kg

Phosphoric acid 300 ml (3ml per litres)

• Here the porous of stones are dried in the open air for 60 to 90 min.

Step # B

• Load the garments treated in step # 1 and step # 2 in a dry m/c. Lot size should be 20 to 30kg.
• Run the m/c for 5 to 7 minutes. Due to the rotation of m/c the socked stones will hit the garments surfaces and the chemicals in the stone will destroy color of the fabric. Multilayer fabric areas like collar, cuff, pocket, pocket side seam etc. area will be brushed more than the single layer areas, therefore more fading effect will be produced in those areas resulting new color effect in the garments.
• Unload the garments and separate the stones from the batch.
• In this stage KMnO₄ and H₃PO₄ reacts with each other and gives Oxygen which oxidize the color. Here a byproduct MnO₂ is produced which should be neutralized.

6KMnO₄ + 4H₃PO₄ = 2K₃PO₄ + Mn₃(PO₄)₂ + 6H₂O + 3MnO₂ + 2O₂

• This MnO₂ is solubilized by Sodium Metabisulfite (Na₂S₂O₅).

Na₂S₂O₅ + H₂O = 2NaHSO₃

NaHSO₃ + MnO₂ = MnSO₄ + NaOH

• Load the garments to the m/c ;
• Add water into the m/c (1:5 liquor ratio, i.e. 500 litres) ;
• Continue the process (12 to 15 rpm) ;
• Add sodium metabisulfite (1 to 2 gpl, i.e. 500 g to 1kg) ;
• Continue the process for 5 to 10 min and then drain the liquor ;
• Hot wash (at 40^o to 50^o C for 5 minutes).

Step # 3 ( Nutralization )

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );
• Add acetic acid ( CH₃COOH ) to liquor (1 to 2 ml per liter, i.e. 500ml to 1liter);
• Continue the process for 10-12 min and then drain the liquor.

Step # 4 ( Brightening treatment)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add Fluorescent Whitening agent/Fluorescent Brighting agent to liquor (% as required );
• Supply steam to raise temperature (80⁰C);
• Continue the process for 10 min and then drain the liquor.

Step # 5 (Softening)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Start m/c running ( 12 to 15 rpm );

• Add softener to the liquor (0.1 to 0.5%, i.e. 100g to 500g);
• Supply steam to raise the temperature (as required 40⁰ to 60⁰C );
• Continue the process (5 minutes) ;
• Drain the liquor and unload the garments.

Limitations of acid wash :

• Acid washed ,indigo dyed denim has a tendency to yellow after wet processing.
• The major cause is residual manganese due to incomplete neutralization, washing or rinsing.

Remedy :

• Manganese is effectively removed during laundering with addition of ethylene-diamine-tetra-acetic acid as chelating agent.
• Acid washing jeans avoided some of problems of stone wash, but come with added danger, expenses and pollution.

STONE WASH

In the process of stone washing, freshly dyed jeans are loaded into large washing machines and tumbled with pumice stone or volcanic rock to achieve a soft hand and desirable look. Variations in compositions, hardness, size shape and porosity make these stone multifunctional. The process is quite expensive and requires high capital investment. Pumice stone give the additional effect of a faded or worn look as it abrades the surface of the jeans like sandpaper, removing some dye particles from the surfaces of the yarn.

Step # 1(Desizing)

• Load the garments into the washing machine (100 kg) ;
• Add water into the machine(1:5 liquor ratio i;e. 500 liters) ;
• Start machine running (12 to 15 rpm) ;
• Add amylase enzyme (1 to 3% i.e.1 to 3 kg) ;
• Add detergent (1% i.e. 1kg) ;
• Supply steam to raise temp.(60°C) ;
• Continue the process for 20 min and then drain the liquor ;
• Hot wash (at temp. of 40°C to 50°C for 5 minutes).

Step # 2 (Stone wash)

• Add Water into the m/c (1:5 liquor ratio, i.e. 500 litres );
• Add pumice stone half of the volume of garments (30 to 15 kg) ;
• Start machine running (12 to 15 rpm) ;
• Add bleaching powder to liquor (4% i.e. 4kg) ;
• Add soda ash (Na₂CO₃) to liquor (8% i.e. 8kg) ;
• Continue the process for 20 min to 40 min and then drain the liquor ;
• Hot wash (at 40°C to 50°C for 5 minutes).

Step # 1(Desizing)

¤ Load the garments into the washing machine (100 kg). ¤ Add water into the machine(1:5 liquor ratio i;e. 500 liters). ¤ Start machine running (12 to 15 rpm). ¤ Add amylase enzyme (1 to 3% I;e.1 to 3 kg). ¤ Add detergent (1% i;e. 1kg). ¤ Supply steam to raise temp.(60°C). ¤ Continue the process for 20 min and then drain the liquor . ¤ Hot wash (at temp. of 40°C to 50°C for 5 min). Step # 2(Stone wash)

¤ Add water into the machine (1:5 liquor ratio, I,e. 500 litres). ¤ Add Pumice stone half of the volume of garments (30 to 50 kg). ¤ Start machine running (12 to 15 rpm). ¤ Add bleaching powder to liquor (4% i.e. 4 kg) . ¤ Add soda ash (Na₂CO₃) to liquor (8% i.e. 8 kg). ¤ Continue the process for 20 to 40 min and then drain the liquor. ¤ Hot wash (at 40°C to50°C for 5 min).

Step # 5(Softening)

¤Add water into the machine(1:5 liquor ratio, i,e. 500 liters). ¤Start machine running (12 to 15 rpm). ¤Add softener to the liquor (0.1 to 0.5%, i,e. 100 g to 500 g). ¤Supply steam to raise the temp. (as required 40° to 60°C). ¤Continue the process (5 min). ¤Drain the liquor and unload the garments .

PUMICE STONE

These are silica-rich, viscous, high temp. melt product of explosive eruption during ascent and expulsion of the earth. These are light weight , highly porous , rocky substances which will float on water . Major pumice stones supplier countries are USA, Turkey, Italy, Iceland , New Zealand, Japan , Indonesia and Philippines. This is one of the important components in the of stone washed apparels. It is used to abrade the surface of the fabric to obtain a surface pattern effect with colour contrast and softer hand. Since the degree of abrasion may varies in different parts of a garments such as trouser leg, button slay and seaming parts, a number of neutral patterns can be formed.

The degree of wash effect depends on stone size , stone ratio , liquor ratio , duration of treatment , amount of garments loaded , garments GSM, etc. Stone size varies from 1 cm diameter to 7 cm . But other washes like sand wash , micro wash, micro sand wash are now referring to use very small size pumice stones .

Selection of stone:

Stone should be selected of the proper hardness , shape and size for the particular end product . It should be noted that large , hard stones last longer and may be suited for heavy weight fabrics only. Smaller , softer stones would be used for light weight fabrics and more delicate items. Stone wt. / fabric wt. = 0.5 to 3/1 it depends on the degree of abrasion needed to achieve the desired result. Stones can be reused until they completely disintegrate or wash down the drain.

Problem caused by stones:

¤Damage to wash machineries and garment due to stone to machine and machine to stone abrasion.

¤Increase in labor to remove dust form finished garments .

¤Water pollution during disposal of used liquor.

¤Back staining and re-deposition.

Back staining or Re-deposition:

The dye removed from denim material after the treatment with cellulose or by a conventional washing process may cause “back staining “ or “re-deposition”. Re-coloration of blue threads and blue coloration of white threads, resulting in less contrast between blue and white threads.

Remedy of back staining :

¤Adding dispersion/suspension agent to wash cycle.

¤Intermediate replacement of wash liquor.

¤Using alkaline detergent like sodium per borate with optical brightener as after wash.

LIMITATION OF STONE WASHING

# Quality of the abrasion process is difficult to control outcome of a load of jeans is never uniform, little percentage always getting ruined by too much abrasion.

# The process is non selective.

# Metal buttons and rivets on the jeans in the washing machines get abraded .

# This reduces quality of the products and life of equipment, and increases production costs.

# Stones may turn into powder during the process of making the garment grayish in color and rough too.

# provides rougher feel than enzyme wash.

# Stone may lead the harm to machine parts.

Microsanding

A fabric finishing process where fabrics are sanded (real sandpaper) to make the surface soft without hair. Can be performed before or after dyeing. In this fabric treatment process, a series of cylindrical rolls in a horizontal arrangement, either wrapped with an abrasive paper or chemically coated with an abrasive are used to create a soft, sueded hand. The denim is pulled over the face of the sand rollers creating a raised surface finishing. Some color reduction is experienced.

There are 3 ways for this technique:

1. Sandblasting.

2. Machine sanding.

3. Hand sanding or hand brushing.

Used in various ways:

# Flat surfaces (tables, ironing boards).

# On the dummy (inflatable dummies, sometimes standing, sometimes flat, sometimes seated).

# Various templates can be used to create a 3D effect.

Sand blasting

Jeans wear treatment that removes color from certain areas, either all over or placed and gives the garment additional softness. Sand is actually shot at the garment with a powerful spray gun. Recent technology has introduced “automatic” sandblasting, in which the jeans hang and rotate continuously.

1. It is purely mechanical process, not using in chemicals.
2. It is a water free process therefore no drying required.
3. Varity of distressed or abraded looks possible.
4. Any number of designs could be created by special techniques.

It is a process applied on denim fabric garments to get heavy faddy effects on particular points. Sand blasting technique is based on blasting an abrasive material in granular, powdered or other form through a nozzle at very high speed and pressure onto specific areas of garment surface to be treated to give the desired distressed/abraded/ used look.

PROCESS:

1. Individual garment to be processed is taken on a table.
2. Air compressor is started and pressure to maintained between 3-4 kg/sq.cm. Air compressor then stores air in the machine cylinder.
3. Aluminum sand or silicon sand, Al₂(SiO₄)_3, is than taken in the chamber of the blasting machine.
4. Sand and compressed air is than sprayed over the garments at specific points by hand spray pipe.
5. Sand pass into the machine by regulating system. The machine comprises a blasting regulator and a hand regulator to control the amount of sand and compressed air respectively.